Blunt-lobed woodsia (Woodsia obtusa) COSEWIC assessment and status report: chapter 11

Technical Summary

Woodsia obtusa

Blunt-lobed woodsia – Woodsie à lobes arrondis

Range of Occurrence in Canada: Quebec, Ontario

Extent and Area Information

Extent of occurrence (EO) (km²) see Distribution section :
14 000 km²
Specify trend in EO :
stable
Are there extreme fluctuations in EO?
no
Area of occupancy (AO) (km²) see Distribution section
<20 km²
Specify trend in AO :
stable
Are there extreme fluctuations in AO?
no
Number of known or inferred current locations :
8 extant
Specify trend in # :
decline (1 population likely extirpated; recent finds simply represent previously undiscovered populations and not newly established populations)
Are there extreme fluctuations in number of locations?
no
Specify trend in area, extent or quality of habitat :
quality will likely decrease

Population Information

Generation time (average age of parents in the population) :
unknown (possibly decades)
Number of mature individuals :
~1400
Total population trend:
uncertain
% decline over the last/next 10 years or 3 generations.
degree of decline uncertain but likely to occur based on the spread of common buckthorn
Are there extreme fluctuations in number of mature individuals?
no
Is the total population severely fragmented?
yes
Specify trend in number of populations :
very small increase but this due to intensive surveys
Are there extreme fluctuations in number of populations?
no

 

List of populations and abundance
Populations Abundance
1. Frontenac Park, ON
64
2. Westport – Sand Lake, ON
499
3. Westport – Rideau Trail, ON
82
4. Foley Mtn Cons. Area, ON
212
5. Gatineau Park (Champlain), QC
likely extirpated
6. Gatineau Park (Eardley), QC
~300
7. Saint-Armand, QC
~40
8. Ch. Saint-Armand, QC
120
9. Frelighsburg, QC
5 - 6

Threats (actual or imminent threats to populations or habitats)

Actual threats: The inferred spread and increase in abundance of the invasive shrub common buckthorn that is likely to occur at the largest site is the most immediate threat; this was probably promoted through human activity.

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: secure
Is immigration known or possible?
possible but unlikely
Would immigrants be adapted to survive in Canada?
yes
Is there sufficient habitat for immigrants in Canada?
likely some
Is rescue from outside populations likely?
possible but not likely

Quantitative Analysis

not available

Current Status

  • COSEWIC: Endangered (2000), Threatened (2007)
  • Ontario: Endangered
  • Quebec: menacée (Threatened)

Status and Reasons for Designation

Status : Threatened

Alpha-numeric code:  Met criteria for Endangered, B2ab(ii,iii,iv,v), but designated Threatened, C2a(i), because most plants are in protected areas or undisturbed sites where recruitment is occurring.

Reasons for Designation: A species with a highly fragmented distribution in Canada where it is known only from southeastern Ontario and southwestern Quebec at eight small localized sites.  One additional population is now considered to be extirpated. The fern occurs almost exclusively on warm and relatively dry calcareous rocky slopes.  The total Canadian population consists of fewer than 1400 mature plants. The primary threat is at the largest population due to the anticipated loss of habitat quality and decline in the fern population as a consequence of the presence and spread of an exotic invasive shrub.  Most sites, however, are in protected areas or undisturbed sites where recruitment is occurring.

Applicability of Criteria

Criterion A: (Declining Total Population): Not applicable.

Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B2ab(ii,iii,iv,v) based on the small area of occupancy, severely fragmented distribution and decline in the area of occupancy with the loss of one population and the inferred additional loss of area of occupancy, quality of habitat, number of populations and number of mature individuals if common buckthorn is allowed to spread at the site of the largest population.

Criterion C: (Small Total Population Size and Decline): Meets Threatened C2a(i) due to the total population size of < 10,000 mature plants, the extinction of one population, and inferred population decline with the spread of common buckthorn at the largest population.

Criterion D: (Very Small Population or Restricted Distribution): Although occurring within a small area of occupancy of < 20 km², most sites are in protected areas or undisturbed sites such that the species does not meet Threatened and is not likely to be become highly endangered within a short period of time.

Criterion E: (Quantitative Analysis): None available.

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